1. Field of the Invention
The present invention relates to a convertible writing instrument which can be transformed into a straight ruler, a compass, a writing instrument with an eraser, serving as a complete stationery box. The present combinational writing instrument is characterized in its writing core member having a hexagon cross section which is removably housed in a two-piece tube which consists of right and left members pivotably hinged together so that the present writing instrument can be converted to a compass with its open angle freely adjusted within the range of 0-180 degrees, and further to an elongated straight ruler with the right and left members arranged in a rectilinear manner, the ruler is marked with both centimeter and inch units for the facility of use. An eraser is also attached at the end of the writing instrument.
2. The Prior Art
It is often encountered by people to use a pen or the like to mark straight lines or circles without a proper ruler and compass at hand when dealing with daily business. To use a name card or a book and coins of different size to mark straight lines and circles can roughly solve the problem but in a limited manner. Furthermore, the measurement of a certain length is not able to be performed as a result of lack of precise instrument.